All I want is to add a button to end a course

Hi there

I've created my first (test) course on Storyline and I'm quite please with it.  No LMS involved at present.  All I want is to be able to add a button to say Course Finished but although adding a button that jumps to the next / another slide is easy, I can't find a trigger option that closes the slides for the trainee.

Am I missing something obvious.

Thanks

Fliss